main{
    padding: 20px;
    // 头部导航
    .headnav{
        display: flex;
        justify-content: space-around;
        border-bottom: 3px solid #e8e8e8;

        a{
            color: #888;
            font-weight: 700;
            line-height: 2.5em;
            
            &.on{
                color: #4f98ff;
                font-size: 18px;
                position: relative;
            }

            &.on::after{
                content: '';
                display: block;
                height: 2px;
                width: 80%;
                background-color: #4f98ff;
                margin: 0 auto;
            }
        }
    }

}